fix: report command permission errors without a traceback

src/dotenv/cli.py

@@ -244,6 +244,9 @@ def run_command(command: List[str], env: Dict[str, str]) -> None:
         except FileNotFoundError:
             print(f"Command not found: {command[0]}", file=sys.stderr)
             sys.exit(1)
+        except PermissionError:
+            print(f"Permission denied: {command[0]}", file=sys.stderr)
+            sys.exit(1)
 
         _, _ = p.communicate()
 
@@ -254,3 +257,6 @@ def run_command(command: List[str], env: Dict[str, str]) -> None:
         except FileNotFoundError:
             print(f"Command not found: {command[0]}", file=sys.stderr)
             sys.exit(1)
+        except PermissionError:
+            print(f"Permission denied: {command[0]}", file=sys.stderr)
+            sys.exit(1)

tests/test_cli_permission.py

@@ -0,0 +1,45 @@
+"""Command-launch permission failures should be CLI diagnostics, not tracebacks."""
+
+import os
+import sys
+
+import pytest
+
+from dotenv.cli import run_command
+from tests.test_lib import run_dotenv
+
+
+@pytest.mark.parametrize("platform", ["linux", "win32"])
+def test_permission_error_is_reported_on_both_launch_paths(
+    monkeypatch, capsys, platform
+):
+    import dotenv.cli as module
+
+    def denied(*args, **kwargs):
+        raise PermissionError(13, "Permission denied")
+
+    monkeypatch.setattr(module.sys, "platform", platform)
+    monkeypatch.setattr(module.os, "execvpe", denied)
+    monkeypatch.setattr(module, "Popen", denied, raising=False)
+    with pytest.raises(SystemExit) as caught:
+        run_command(["no-execute"], {"PRIVATE_TOKEN": "must-not-appear"})
+    assert caught.value.code == 1
+    output = capsys.readouterr().err
+    assert "Permission denied: no-execute" in output
+    assert "must-not-appear" not in output
+
+
+@pytest.mark.skipif(sys.platform == "win32", reason="POSIX execute bits")
+@pytest.mark.parametrize("target_kind", ["file", "directory"])
+def test_run_nonexecutable_target_has_no_traceback(tmp_path, target_kind):
+    (tmp_path / ".env").write_text("A=b\n")
+    target = tmp_path / "not-executable"
+    if target_kind == "file":
+        target.write_text("#!/bin/sh\nexit 0\n")
+        target.chmod(0o600)
+    else:
+        target.mkdir()
+    result = run_dotenv(["run", os.fspath(target)], cwd=tmp_path)
+    assert result.returncode == 1
+    assert "Permission denied:" in result.stderr
+    assert "Traceback" not in result.stderr